Electronic and ionic conductivity are one of the most important phenomena in the fields of energy materials, sensor devices, biological systems and so on. It is not only important for the efficiency of charge transport, but also relates to the chemical and electrochemical reaction mechanism and rates within the systems. At the meantime, it is also one of the determinative factors for the construction of electrochemical boundaries, and then dominates the performance, cost, and durability of the applied devices. In the fields of advanced energy technologies, including fuel cells, metal-air batteries and lithium ion batteries, the synergy of electron and ion transport is the key factor limiting the development. Therefore, efficient detection of ionic conductivity and electronic conductivity, as well as effective analysis of charge transport channels, is one of the key technologies for synthesis of electrode materials and structures.
The traditional measurements of electronic and ionic conductivity include the two-electrode and four-electrode ohms or electrochemical methods. With years of development, these techniques have been evolved as mature detection systems, and gained success in theoretical and applied aspects. However, in the current electrochemical systems including fuel cells, lithium ion batteries, and electrochemical sensors, the functions of electronic and ionic conductance usually exist synchronously in the microstructure of the electrode in the form of compound channels to ensure the high efficiency and utilization of the electrochemical boundaries and active components. Therefore, in the systems integrated with both the electronic and ion conductivity, it was found difficult to separate ionic conductance from the complicated series and parallel connections of electronic and ionic conductors with the traditional measurement equipped with metal probes. Specifically, the electronic conductivity of the electrode is usually greater than 1 S/cm, generally up to 10-103 S/cm, much higher than the ionic conductivity in the magnitude order of 10−3-10−1 S/cm range. Conventional conductivity testing methods could hide signals of the ion conductance, and then render it impossible to separate efficiently. For this reason, finding a way to effectively separate the electronic conductance from the ionic conductance is critical to the development of advanced materials. On the other hand, the traditional ionic conductance detections are usually performed in the aqueous solution, which obviously differ from the applied environment in the electrode system and hardly reflect the convincible property of the ionic conductance. Therefore, the design and preparation of an conductivity testing instrument with controllable temperature and humidity could lay the foundation of analytical techniques for the development of electrode materials.